Perhaps you might want to do a little research. Old apps can stay as they are UNLESS they summit an update, upon an update submission, the app MUST support the iOS8 SDK. This is an apple rule. You need to take this with Apple and not DIRECTV®
Existing apps are only affected if they want to submit feature or bug fix updates. Apple will not remove any apps currently on the store today. Luckily, complying to this rule is not particularly difficult. Adding 64-bit support to an app usually only takes a few days of development time at most, even with a big project.